Seal assembly

ABSTRACT

A seal assembly for sealing at least one negative or positive pressure zone which adjoins a surface which is perforated and moves in a movement direction in a machine for making paper, tissue or cardboard, has at least one sealing element which lies opposite the moving surface and is arranged in a receptacle which can be moved to change the format of the negative or positive pressure zone. In order to simplify the adjustability of the receptacle in order to position the sealing element, there is a signal transmitter which is connected directly or indirectly to the sealing element and the signal of which can be received on that side of the moving surface which faces away from the sealing element.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of PCT application No. PCT/EP2012/058874,entitled “SEAL ASSEMBLY”, filed May 14, 2012, which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a seal assembly for sealing at leastone negative or positive pressure zone which adjoins a perforatedsurface which moves in a movement direction in a paper, tissue orcardboard machine.

2. Description of the Related Art

In practical applications seal assemblies of this type are used in theforming section as well as in the press section and/or the dryingsection of a respective paper machine, where they can be utilized insuction rolls or blow rolls.

Suction rolls of this type can, for example, be used as a pick-upsuction roll or as a suction guide roll. There are applications whereinthe paper, tissue or cardboard web—referred to in this document simplyas a web—runs with or without support of fabrics or felts. The suctionrolls comprise, as a rule, stationary inside suction boxes, which formfor example adjustable zones with at least one pressure level. Sealingof the pressure- or vacuum zones in the direction of fabric travel andin the axial direction occurs through sealing elements which, ifpositionable, can be mounted in adjustable receptacles, for exampleso-called “format slides”. The moving surface in this case is consistentwith the inside surface of the roll shell and as a rule is curvedcircularly.

The sealing elements which, due to their elongated shape, are alsoreferred to as sealing strips contact the roll shell at the edge of apositive or negative pressure zone in the axial direction as well asalso in the circumferential direction and thereby seal the zone. The webis held in the circumferential region of the negative pressure zone onthe roll circumference through suction bores in the roll shell. Thesuction chamber often serves to also extract moisture from the web.

A suction roll is known from DE 10 2009 000 371 A1 whose suction boxformat is changeable through sealing element receptacles which laterallylimit the suction zone and which are adjustable axially as well as incircumferential direction.

In order to achieve high running time efficiency it is important, amongother things, to ensure a stable web run. Nevertheless, in many, inparticular in graphic paper machines, web run problems occur. Therefore,after separation from the felt, in other words lifting of the felt onone web side or lifting of the web edge off of the felt, an unstablepaper edge or even a raised edge, manifests itself.

Tests have shown that the adjustment of the suction on the web with thesuction rolls, in particular with the suction felt guide roll has asignificant influence on the edge characteristics of the paper. In orderto ensure an optimum vacuum build-up on the paper, the “format slides”on the suction felt guide rolls and the pick-up rolls must be adjustedprecisely, in particular transverse to the direction of web travel, inother words axially.

In machines currently in use however, the exact position of the formatslide relative to the paper edge is not known since the adjustment ofthe web width occurs earlier in the production sequence, at the former(edge seam) and is not in direct relation to the adjustment of theformat slide. In order to establish the position, the web edge must bedetermined relative to a fixed point of the roll (for example the rolledge). Then, the relative distance of the format slide to the paper edgemust be determined by means of the geometric design data of the roll.This process is time consuming and at the same time awkward. If duringthe life span of a felt, adjustments are made to the edge seam, then theweb width changes and the relative format slide positions becomeincreasingly obscure if the adjustment is not reacted to immediately.

What is needed in the art is to simplify the adjustability of thereceptacle for positioning the sealing element.

SUMMARY OF THE INVENTION

The present invention provides a signal transmitter connected directlyor indirectly with the sealing element, the signal of which can bereceived on the side of the moving surface facing away from the sealingelement. The term “direct or indirect” in this case is intended to statethat the signal transmitter is connected directly with the sealingelement or its retainer, or that additional components, for examplelinkages, are arranged between them. In each case however, together witha movement of the sealing element or respectively its receptacle, thesignal transmitter should also be moved.

The fact that the signal is received on the side of the moving surfacefacing away from the sealing element has many advantages. This fact isdescribed in further detail below with an example of a suction roll. Themoving surface in this case corresponds to the inside wall of aperforated suction roll shell. If the signal transmitter is connectedwith the sealing element then it provides precisely the current positionof the sealing element which, therefore, according to the presentinvention can also be determined outside the roll shell.

Sealing elements such as can be used for the present invention areknown. They consist, for example, of strip shaped rubber graphite orfiber reinforced thermosetting plastics.

The term “signal” can be defined broadly. The signal may occur throughelectromagnetic radiation, acoustic transducers but also through fluidflows. It is important that it can pass through the roll shell, forexample through the perforation, and that it can be received from theoutside of the roll.

The signal transmitter is, for example, at least one light source suchas a light beam. The signal transmitter is, therefore, a cost effectiveand simple component. The light beam, in other words the signal, canpass through the perforation and can be captured by the human eyewithout technical receivers.

The light source may, for example, be provided by a laser. The highintensity of the light beam and its concentration offers the advantageto be able to micrometer-precisely recognize the location of the laserinside the roll, and thereby also to be able to precisely determine thelocation of the sealing element connected with it.

As has been shown in trials, intensity of the light beam and itsconcentration further offer the great advantage that the light isclearly visible not only through the perforation, but also through theweb and even through a potentially utilized felt. A web edge, forexample, and a sealing element extending in the circumferentialdirection can thereby be precisely adjusted to each other.

Further, the signal transmitter may be arranged inside the sealingelement. In this way the exact location of the sealing element can bedetermined directly and without relative spacing.

A bore is, for example, provided in the sealing element through whichthe signal can pass. The signal transmitter can therefore beaccommodated at a certain depth in the sealing element. This isadvantageous since the section above is generally subject to wear andtear due to friction on the inside wall of the shell. The signaltransmitter is therefore located in a protected region.

At least the bore may, for example, be filled with a material whichpermits the signal to pass through. This prevents the bore from cloggingwith abraded materials or other dirt. In the case where the signaltransmitter is a light source, a transparent synthetic glass could, forexample, be used for this purpose. The term “at least” in this contextis meant to indicate that also the entire sealing element could consistof a material which allows the signal to pass through.

Alternatively, it is feasible to provide the bore with a flushingdevice. A connection for a water supply could, for example, be provided.This flushing would provide the additional advantage that the gap at thesealing element to the shell is thereby lubricated and wear and tear onthe sealing element would thus be reduced.

The receptacle may be movable through a servomotor. Such a servomotorcould be an electrically driven motor driving a spindle or, for example,a hydraulic or pneumatic cylinder. This servomotor provides theadvantage that the receptacle can be readjusted at any time withouthaving to make a manual adjustment via a normally utilized spindle whichis accessed from the outside or by even having to open up the roll.

Provision is made that the signal from the signal transmitter can bepicked up by a receiving unit which is connected with a microprocessor.In the case where the signal transmitter is a light source this could bean optical sensor. In this manner continuous monitoring duringproduction is possible to ascertain whether the desired position of thesealing element is being kept. If this is not the case, themicroprocessor can issue a warning or may even ensure through control ofa servomotor on a receptacle that the sealing element is moved into thecorrect position. In addition, an inadvertent wrapping of the roll withthe web can be monitored, since the received signal would weaken orfluctuate during a wrap-up.

The signal transmitter, the receiving unit and the servomotor may becomponents of a closed control circuit. The personnel can then operatethe paper machine in the region of the suction roll fully automated witha suitable microprocessor program which determines the upper limitingvalues for the distance between web edge and sealing element, dependingon paper quality, moisture or weight of the web or additionalparameters.

A seal assembly with a plurality of signal transmitters and possibly acorresponding number of receiving units is also to be covered by thepresent invention. It can be useful to equip the sealing elements with aplurality of signal transmitters, for example due to redundancy.Moreover, a plurality of signal transmitters can more easily considerboth web edges or, respectively, additional sealing element locations.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of (an) embodiment(s) of the invention taken in conjunctionwith the accompanying drawing(s), wherein:

FIG. 1 is a schematic example of a seal assembly according to thepresent invention with an optical signal transmitter; and

FIG. 2 illustrates a three-dimensional section of a suction rollaccording to the current state of the art, on which the perforated shellhas been removed.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplification set out hereinillustrates one embodiments of the invention and such exemplification isnot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 2, it isnoted that FIG. 2 serves the explanation of the problem which is thebasis of the present invention and illustrates the interior of suctionroll 2 with seal assembly 1. A perforated shell 3 which is notillustrated rotates around support 6 which includes all parts notrotating during operation. Negative pressure zones 7.1, 7.2, as well asall supply and outlet lines, and mechanical regulating devices areprovided on support 6.

Suction roll 34 includes a first, at least substantiallyhorseshoe-profiled or U-shaped suction zone 7.1 with two lateral suctionzone sections 21.1, 21.2 as limbs, extending respectively generally in aroll circumference direction, and one suction zone section 21.3connected with them, extending generally parallel to the roll axis. Thisfirst suction zone 7.1 can be provided as a high vacuum suction zone.

The format measured in the axial direction is variably adjustablethrough two lateral axially outer movable receptacles 8 which aremovable, for example on rods 22, simultaneously or independent from eachother. The remaining retainers are stationary retainers 9 for sealelements 10.

A holding zone 7.2 can be provided between suction zone sections 21.1and 21.2.

As is known from DE 10 2009 000371 A1, additional movable receptacles 8may be provided which are not illustrated here. These can also bearranged to pivot around the roll axis so that a different length of anunder pressure zone 7.1, 7.2 can be achieved in the direction ofmovement 25 of the shell. Moreover, an additional suction zone may beprovided following first suction zone 7.1, viewed in the circumferentialdirection.

Up to this point the description of FIG. 1 of a suction roll 2 with aseal assembly 1 corresponds to the current state of the art, whereby theedge of a web cannot necessarily be allocated to the position of asealing element.

In order to explain the present invention which eliminates thisshortcoming, FIG. 1 needs to be considered, which has schematicallyassumed the main components of FIG. 2 which are essential for thepresent invention and which in addition illustrates the featuresaccording to the present invention.

One can see the seal assembly 1 with shell 3 moving in the direction ofmovement 25 (arrow pointing away from sheet plane). The inside wallrepresents moving surface 4 which is part of the present invention.Shell 3 is equipped with suction bores 5, only one of which isillustrated for the sake of clarity. The suction bores hold the web onthe outer roll shell, as well as supply air and moisture into underpressure zone 7.1.

In a purely schematic depiction, movable receptacle 8 is illustratedU-shaped. It accommodates sealing element 10 consisting of rubbergraphite. Light source 12 in the form of a laser is inserted in thelower region of sealing element 10. The emitted light beam 24 isindicated by a dotted line. (In other embodiments anotherelectromagnetic radiation, an acoustic sound or a particle beam couldalso be emitted). The light beam passes through rotating shell 3intermittently, in other words always exactly at an oppositely locatedsuction bore. An observer therefore knows exactly where the seal elementis located and can determine the position relative to the edge of web23. If required, receptacle 8 of seal element 10 can easily bereadjusted at the desired location. This occurs, for example through aservomotor 17.

This process can however also be automated and regulated if receivingunit 18 (in this embodiment where the signal transmitter 11 is lightsource 12, in other words a light-sensitive sensor) is used. The signalsof receiving unit 18 can be evaluated by microprocessor 19 andappropriate positioning commands be transmitted to servomotor 17. Signalline 20 for this is indicated by a dashed-dotted line.

Laser 12 is arranged in the lower region of sealing element 10, so thatit is not affected by wear and tear at moving surface 4 of shell 3. Thelight beam therefore passes through a bore 13. Bore 13 can be filled,for example with an acrylic, in other words with a material which ispermeable to the signal, in this case light. This avoids dirt build upin bore 13. Bore 13 can alternatively also be provided with flushingdevice 14. Water, for example is thereby supplied through supply line 15into the bore where it discharges again in seal gap 16. This providesthe additional positive effect that a hydrostatic lubrication isestablished between seal element 10 and moving surface 4.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

COMPONENT IDENTIFICATION LIST

-   1 seal assembly-   2 suction roll-   3 shell-   4 moving surface-   5 suction bore-   6 support-   7.1, 7.2 under pressure zone (or over pressure zone)-   8 movable receptacle-   9 stationary retainer-   10 sealing element-   11 signal transmitter-   12 light source, laser-   13 bore in seal element-   14 flushing device-   15 supply line-   16 seal gap-   17 servomotor, cylinder-   18 receiver-   19 microprocessor-   20 signal line-   21.1, 21.2, 21.3 suction zone section-   22 rod-   23 web-   24 light beam-   25 direction of movement

What is claimed is:
 1. A seal assembly for sealing at least one negativepressure zone or positive pressure zone adjoining a perforated surfaceand moving in a movement direction in a fibrous web machine, the sealassembly comprising: a receptacle movable to change a format of thenegative pressure zone or the positive pressure zone; a moving surface;at least one sealing element located opposite said moving surface, saidat least one sealing element being arranged in said receptacle; a signaltransmitter connected directly or indirectly with said at least onesealing element, a signal from said signal transmitter being receivableon a side of said moving surface facing away from said at least onesealing element.
 2. The seal assembly according to claim 1, the fibrousweb machine being one of a paper machine, a tissue machine and acardboard machine.
 3. The seal assembly according to claim 1, whereinsaid signal transmitter is at least one light source.
 4. The sealassembly according to claim 3, wherein said at least one light source isprovided by a laser.
 5. The seal assembly according to claim 1, whereinsaid signal transmitter is arranged inside said at least one sealingelement.
 6. The seal assembly according to claim 1, further comprising abore in said at least one sealing element, said bore being arranged suchthat said signal can pass through said bore.
 7. The seal assemblyaccording to claim 6, said bore being at least one bore filled with amaterial permeable to said signal.
 8. The signal assembly according toclaim 7, said at least one bore further including a flushing device. 9.The signal assembly according to claim 8, said receptacle being movableby a servometer.
 10. The seal assembly according to claim 9, furthercomprising a receiving unit connected with a microprocessor, said signalfrom said signal transmitter being capable of being picked up by saidreceiving unit.
 11. The seal assembly according to claim 10, said signaltransmitter, said receiving unit and said servomotor being components ofa closed control circuit.